Numerous manufacturing processes require the use of means of distributing streams or flows of fibrous material to produce the desired end product. Often, the process for manufacturing fibrous material results in a flow of fibrous material having a generally non-uniform fiber distribution which is not easily collected into a final product having a uniform thickness and density. Also, typical flows of fibrous materials generated from fiber manufacturing steps frequently have a cross-sectional width which is narrow relative to the width ultimately desired for the final product. Consequently, the fibers must be distributed to make an acceptable product.
Mineral fibers can be made from molten mineral material, such as glass, using any one of several well known processes, such as the rotary process. The rotary process results in a downwardly moving, cylindrically shaped flow of glass fibers and gases, commonly referred to as a veil. An example of a flow of fibers requiring distribution is the veils of glass fibers produced in the manufacture of mineral fibers, such as glass fibers. There is a need to distribute and disburse the fibers to form a wide blanket or pack having a generally uniform thickness and density.
Numerous devices have been used in the past to effect uniform distribution of flows of fibrous materials, including baffles, chutes, Coanda surfaces, mechanical lappers, air nozzles and air knives. Typically, a fibrous flow or veil is impinged upon by opposed lapping devices, such as air nozzles. The opposed lapping devices operate alternately to distribute the fibrous material back and forth across the width of a moving collection surface. When an oscillating surface or pulsating air jets from air nozzles or air knives are used, there is an inherent limitation on the effective frequency of the lapping or distributing device. Mechanical inertia limits mechanical lapping devices, and air driven lappers are usually limited by inertia and accumulator effects. The highest effective frequency of known mechanical or air jet lapping devices is about 1 to 2 hz.
One technique used in the past to help the process of distributing fibrous flows, particularly cylindrically shaped fibrous flows, is the use of a pair of opposed foraminous drums which flatten the fibrous flow and remove much of the air flowing with the fibers. The flattened fibrous flow should be easier to distribute because much of the air has been removed. A recent improvement in the use of foraminous drums is to operate the drums at a very high speed, with the tangential rate of the drum surfaces approximating the speed of the fibers in the fibrous flow. The use of high speed drums is disclosed in more detail in U.S. patent application Ser. No. 08/236,067, filed May 2, 1994, naming Aschenbeck et al. as inventors, and hereby incorporated by reference. The flattened veil from the foraminous drums is believed to be easier to distribute or lap from side to side because most of the air has been removed from the flow of fibers.
A problem with using high speed drums is that the material is delivered from the drums faster than it can be effectively collected, or faster than it can be collected in a uniform manner. It would be highly desirable to be able to lap the fibrous flows at a rate faster than that allowed by conventional lapping techniques. Lapping at faster rates would lead to more uniform distribution of the fibrous material in the final product.
Another problem with conventional lapping techniques is that the fibrous products tend to be uneven in weight, thickness and density across the width of the product. It would be desirable to have a distribution or lapping technique for high speed veils or flows of fibers which results in a uniform laydown or distribution of fibers, without wrinkling or stretching of the fibrous material.